The invention is an optical imager for use in birefringent detector acoustic imaging systems. In birefringent detector acoustic imaging systems acoustic energy produced by an acoustic source is transmitted through a coupling medium, interacts with an object being imaged, is transmitted through the coupling medium, interacts with a birefringent medium contained in a birefringent detector chamber with the acoustic energy changing the birefringence of the birefringent medium so that an image can be formed by an optical imager, whereupon the image can be processed by a data processor and input to an image output device.
Several features of birefringent detector acoustic imaging systems have been disclosed by Sandhu in U.S. Pat. Nos. 4,379,408, 4,393,712, 4,492,107, 4,506,550, 4,530,242, 4,652,086, 4,651,567, 4,679,436, 4,788,865, and 5,796,003 (which are incorporated herein by reference); by Dreyer in U.S. Pat. No. 3,597,043, by Greguss in U.S. Pat. No. 3,831,434, by Dion in U.S. Pat. No. 4,338,821, by Robillard in U.S. Pat. No. 4,905,202; and by Sandhu et. al. in: "Ultrasonic inspection of tight-radii in composites using acoustography," Proceedings of SPIE, Vol. 3396 pp. 169-179, 1998; "Recent Progress on Ultrasonic NDE Using Acoustography," Second Conference on NDE Applied to Process Control of Composite Fabrication, Nondestructive Testing Information Analysis Center, pp. 229-237, Austin, Tex., 1996; "Acoustography for rapid ultrasonic inspection of composites," Proceedings of the Nondestructive Evaluation Techniques for Aging Infrastructure & Manufacturing, Scottsdale, Ariz., Pub. SPIE, December 1996; "Acoustography," Special nondestructive testing methods, Nondestructive Testing Handbook, 2.sup.nd ed., P. O. Moore and P. McIntire eds., 9, pp. 278-284, American Society for Nondestructive Testing, Columbus Ohio, 1995.
Outstanding problems have prevented workers from devising commercially useful systems. Systems had not been sufficiently sensitive so that useful images could be obtained with sufficiently low cost in time and money. The optical imager shown here improves the optical imaging by having all of the rays of the light interacting with the birefringent detector be at the same predetermined optimum angle relative to the normal axis of the birefringent detector so that useful images are obtained at sufficiently low cost in time and money. This improvement is not suggested in any prior art nor in any combination of prior art.